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A relatively small-size packaged gas engine cogeneration system, CO-204G (rated electric output: 15 kW), was developed as an energy saving device for commercial businesses. The main technological development targets were to realize a compact and low-noise package to fit urban environment, and to achieve a 4,000-hour maintenance interval. Various technologies were developed and tested to realize these targets. Actual operating performance of the packages, which were introduced into market was investigated. The energy-saving effect of the package was verified by these results.

Recently, the demand for comfort with environmental protection has been increasing considerably. This is not only the concern of industry, but also of the entire society. Therefore, it's required as an indispensable element for engines as power sources of machineries to have characteristics such as low noise and pollution output, as well as high performance and reliability. There have been various studies on this theme and steady achievements have been made so far. However, the conventional technologies have their limitations, having reached the highest level that they can possibly achieve, so now new technologies and new thinking are needed to meet the environmental theme. This report discusses a new approach to the 92.4mm Stroke Series next generation engines, which have reduced noise by using noise quality analysis and other techniques. This report also presents the optimization of the combustion system by utilizing numerical simulation techniques such as fluid flow analysis.

WE HAVE DEVELOPED AND MERCHANDISED OIL AND AIR-COOLED DIESEL ENGINES, “OC SERIES”, TO MEET THE NEEDS FROM THE PUBLIC FOR LOWER LEVELS OF NOISE AND EMISSION. AIMED TO REDUCE NOISE TO THE LEVEL OF A WATER-COOLED DIESEL ENGINE AND TO REDUCE SIZE AND WEIGHT TO THOSE OF AN AIR-COOLED GASOLINE ENGINE, THIS IS A SERIES OF ENGINES MOST SUITABLE TO THE WORLD MARKET FOR SMALL-SIZED ENGINES. IN ORDER TO REALIZE LOW NOISE AND LOW EMISSION, THE TVCS COMBUSTION SYSTEM IS EMPLOYED. ITS OIL-COOLED COMBUSTION CHAMBER ENABLES AN SWIRL-CHAMBER COMBUSTION SYSTEM WHICH ALLOWS FOR HIGH OUTPUT. WEIGHT HAS BEEN REDUCED TO LIGHT WEIGHT WITH THESE ENGINES BY ADOPTING DESIGN SIMILAR TO THAT OF AIR-COOLED ENGINES INCLUDING THE USE OF A SIDE-COVER TYPE CRANKCASE. FURTHERMORE, COLD STARTING IS ENABLED WITH THE RECOIL STARTER ALSO FOR HAND-STARTING IDI DIESEL ENGINE, WHICH HAS BEEN REGARDED AS RELATIVELY DIFFICULT DUE TO ITS HIGH COMPRESSION RATIO.

With a drastic advance of computing software and hardware, recently, simulation techniques play snore important role in development and design of diesel engines. Especially, Finite Element Method (FEM) is indispensable for design of diesel engine components, as a tool of optimizing each part and selecting the Materials. Meanwhile, it is one of the greatest theme for all engine designers to raise compactability and high-performance of small engines. At the same time, we have to respond to social needs, that is safety, reliability, durability, and comfortability, for reduction of noise and vibration. Moreover, for design of engine components, we always try to reduce a period of development and make more economical components because we have to consider those cost. To meet this severe requirement, it is needed not to apply the simulation techniques just as they are, but to establish the higher and more useful ones.

Since Kubota introduced its first production of small-sized, multi-cylinder diesel engine series. such as 82mm stroke and 70mm stroke in 1971, Kubota has been producing them for Kubota's own farm machinery and for general industrial applications. The engines have been under continuous development since production began. During this period, production numbers reached approximately 1.7 million units (6 million cylinder) in total. Further, Kubota, taking advantage of such levels of production, developed another series of 73.6mm/78.4mm stroke IDI engines which are applicable to the industrial market. In this paper, the writers explain the engines' various features such as “excellent power/torque characteristic”, “light and compact”, “low fuel consumption”, “low noise”,” good starting characteristic”, and “easy maintenance” and also describe how such achievements have been done, as well as describing the engines' basic structural characteristics.

The 82-Stroke DI (direct injection) engine has been under development at Kubota for years. Production was started in March, 1983 for installation in Kubota tractors as its first application and the cumulative production reached about 120,000 units by the end of 1986. With this performance, as a background, the launching of this DI engine into the general industrial engine market is scheduled for 1987. This new engine series is the DI version of Kubota 82-Stroke IDI (indirect injection) engine series which has reached a cumulative production of about 700 thousand units. As such, the new engine series has the dependability of the use-tested basic engine construction plus the additional features of “excellent torque characteristic”, “low fuel consumption”, “good starting characteristic” and “oil maintenance reduced to a half”.